’s. However, in the case of the matter-tensor
, the case is not yet quite clear; and we shall see that opinion is divided on the subject. In order to understand the point at issue, let us turn once more to the gravitational equations in the interior of matter:
There are ten separate equations corresponding to the ten separate components of the second-order symmetrical tensors
and
. If we assume that a certain definite mesh-system has been chosen, or, again, that the observer is specified, each one of the ten components of